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Find video protocols related to scientific articles indexed in Pubmed.
Strong underwater adhesives made by self-assembling multi-protein nanofibres.
Nat Nanotechnol
PUBLISHED: 08-14-2014
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Many natural underwater adhesives harness hierarchically assembled amyloid nanostructures to achieve strong and robust interfacial adhesion under dynamic and turbulent environments. Despite recent advances, our understanding of the molecular design, self-assembly and structure-function relationships of these natural amyloid fibres remains limited. Thus, designing biomimetic amyloid-based adhesives remains challenging. Here, we report strong and multi-functional underwater adhesives obtained from fusing mussel foot proteins (Mfps) of Mytilus galloprovincialis with CsgA proteins, the major subunit of Escherichia coli amyloid curli fibres. These hybrid molecular materials hierarchically self-assemble into higher-order structures, in which, according to molecular dynamics simulations, disordered adhesive Mfp domains are exposed on the exterior of amyloid cores formed by CsgA. Our fibres have an underwater adhesion energy approaching 20.9?mJ?m(-2), which is 1.5 times greater than the maximum of bio-inspired and bio-derived protein-based underwater adhesives reported thus far. Moreover, they outperform Mfps or curli fibres taken on their own and exhibit better tolerance to auto-oxidation than Mfps at pH???7.0.
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Infrared emitting quantum dots: DNA conjugation and DNA origami directed self-assembly.
Nanoscale
PUBLISHED: 03-18-2014
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QDs that emit in the infrared (IR) range are of special interest at the moment because of their potential as tissue imaging reagents. Due to autofluorescence from tissues, QDs that emit in the visible range fail to produce good signal to noise ratios. Here we report the production of Cd(x)Pb(1-x)Te tertiary-alloyed QDs that emit in the 1100-1300 nm wavelength range, capped with the hydrophilic ligands mercaptopropionic acid (MPA) or glutathione (GSH), together with DNA, as specific surface tags. We observed an interesting dependence of the QD emission peaks on the species of capping ligand used. ICP-MS analysis confirmed that changing the identity of the surface ligand in the reaction mixture shifted the elemental composition of the particles and resulted in different Cd/Pb ratios. Further, DNA directed assembly of the particles onto DNA nanostructures ensures that the particle remains stable in high salt conditions, which is crucial to biological applications.
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Synthesis and patterning of tunable multiscale materials with engineered cells.
Nat Mater
PUBLISHED: 02-11-2014
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Many natural biological systems--such as biofilms, shells and skeletal tissues--are able to assemble multifunctional and environmentally responsive multiscale assemblies of living and non-living components. Here, by using inducible genetic circuits and cellular communication circuits to regulate Escherichia coli curli amyloid production, we show that E. coli cells can organize self-assembling amyloid fibrils across multiple length scales, producing amyloid-based materials that are either externally controllable or undergo autonomous patterning. We also interfaced curli fibrils with inorganic materials, such as gold nanoparticles (AuNPs) and quantum dots (QDs), and used these capabilities to create an environmentally responsive biofilm-based electrical switch, produce gold nanowires and nanorods, co-localize AuNPs with CdTe/CdS QDs to modulate QD fluorescence lifetimes, and nucleate the formation of fluorescent ZnS QDs. This work lays a foundation for synthesizing, patterning, and controlling functional composite materials with engineered cells.
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DNA directed self-assembly of anisotropic plasmonic nanostructures.
J. Am. Chem. Soc.
PUBLISHED: 10-17-2011
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Programmable positioning of one-dimensional (1D) gold nanorods (AuNRs) was achieved by DNA directed self-assembly. AuNR dimer structures with various predetermined inter-rod angles and relative distances were constructed with high efficiency. These discrete anisotropic metallic nanostructures exhibit unique plasmonic properties, as measured experimentally and simulated by the discrete dipole approximation method.
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Colloidal synthesis of metastable zinc-blende IV-VI SnS nanocrystals with tunable sizes.
Nanoscale
PUBLISHED: 09-14-2011
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Here we report the colloidal synthesis of size-tunable SnS nanocrystals that have an unusual meta-stable cubic zinc-blende phase instead of the more stable layered orthorhombic phase. The single-crystalline zinc-blende SnS nanocrystals with sizes of 8 nm, 60 nm, and 700 nm were achieved by injecting the sulfur-oleylamine precursor into tin-oleylamine solution in the presence of hexamethyldisilazane (HMDS) at different temperatures. The morphology and structure of the SnS nanocrystals were studied by high-resolution electron microscopy techniques. The small SnS nanoparticles (?8 nm and ?60 nm) are nearly spherical and have the polyhedral shape. The large (?700 nm) crystals display a unique crystal morphology that have T(d) symmetry with a truncated tetrahedron configuration, and the four truncated surfaces each outgrow to form a convex triangular pyramid corner. Careful structural analysis revealed that each of the crystal is enclosed by 4 low-index {111} hexangular facets and 12 high-index {220} triangular facets using a lift-out technique with a focused ion beam (FIB) and followed by high resolution electron microscope imaging. The direct band gaps of the different sized SnS nanocrystals range from 1.63 eV to 1.68 eV. These heavy-metal-free and low cost nanocrystals are highly efficient absorptive materials in the whole UV-visible range, suitable for applications in photovoltaic cells.
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DNA origami with complex curvatures in three-dimensional space.
Science
PUBLISHED: 04-16-2011
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We present a strategy to design and construct self-assembling DNA nanostructures that define intricate curved surfaces in three-dimensional (3D) space using the DNA origami folding technique. Double-helical DNA is bent to follow the rounded contours of the target object, and potential strand crossovers are subsequently identified. Concentric rings of DNA are used to generate in-plane curvature, constrained to 2D by rationally designed geometries and crossover networks. Out-of-plane curvature is introduced by adjusting the particular position and pattern of crossovers between adjacent DNA double helices, whose conformation often deviates from the natural, B-form twist density. A series of DNA nanostructures with high curvature--such as 2D arrangements of concentric rings and 3D spherical shells, ellipsoidal shells, and a nanoflask--were assembled.
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High-quality manganese-doped zinc sulfide quantum rods with tunable dual-color and multiphoton emissions.
J. Am. Chem. Soc.
PUBLISHED: 03-15-2011
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We report a simple, fast and green phosphine-free colloidal chemistry to synthesize high-quality wurtzite-type Mn-doped ZnS quantum rods (QRs) with tunable diameters (1.6-5.6 nm), high aspect ratios (up to 50), variable Mn doping levels (0.18-1.60%), and high quantum yields (up to 45%). The electron paramagnetic resonance spectra with modeling reveal the successful doping of paramagnetic Mn(2+) ions in the host ZnS QRs. The Mn-doped ZnS QRs demonstrate tunable dual-color (orange and blue) emissions by tuning the doping levels and UV excitation wavelengths. The orange emission with long decay lifetime (3.3 ms) originates from the doped Mn(2+) states, while the blue emission with fast decay lifetime (0.31 ns) is attributed to the QR surface states. The bright two- and three-photon excitation upconversion luminescence from the Mn-doped ZnS QRs have been observed using tunable near-infrared femtosecond laser. Our strategy provides a versatile route to programmably control the optical properties of anisotropic semiconductor nanomaterials, which may create new opportunities for photonic devices and bioimaging applications.
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Surfactant-free self-assembly of nanocrystals into ellipsoidal architectures.
Chemphyschem
PUBLISHED: 11-16-2010
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A simple approach to control the self-assembly of ZnS nanocrystals into well-defined, uniform, three-dimensional, micrometer-scale, solid ellipsoidal structures with rattle-type, multishelled, and hollow architectures is presented. There is no surfactant or small molecule to assist the self-assembly of the nanocrystals. A possible mechanism of the controlled self-assembly is proposed. The growth process can be divided into two stages: 1) the formation of ellipsoidal architectures via oriented aggregation, the growth kinetics of which is primarily attributed to the charge-charge, charge-dipole, and dipole-dipole interactions of preformed ZnS nanocrystals; and 2) Ostwald ripening, which results in multishelled, rattle-type, and hollow structures. This self-assembly concept is also applicable to other metal sulfides.
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Aqueous synthesis of zinc blende CdTe/CdS magic-core/thick-shell tetrahedral-shaped nanocrystals with emission tunable to near-infrared.
J. Am. Chem. Soc.
PUBLISHED: 04-07-2010
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We demonstrate the synthesis of near-IR-emitting zinc blende CdTe/CdS tetrahedral-shaped nanocrystals with a magic-sized (approximately 0.8 nm radius) CdTe core and a thick CdS shell (up to 5 nm). These high-quality water-soluble nanocrystals were obtained by a simple but reliable aqueous method at low temperature. During the growth of the shell over the magic core, the core/shell nanocrystals change from type I to type II, as revealed by their enormous photoluminescence (PL) emission peak shift (from 480 to 820 nm) and significant increase in PL lifetime (from approximately 1 to approximately 245 ns). These thick-shell nanocrystals have a high PL quantum yield, high photostability, compact size (hydrodynamic diameter less than 11.0 nm), and reduced blinking behavior. The magic-core/thick-shell nanocrystals may represent an important step toward the synthesis and application of next-generation colloidal nanocrystals from solar cell conversion to intracellular imaging.
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Gold nanoparticle self-similar chain structure organized by DNA origami.
J. Am. Chem. Soc.
PUBLISHED: 02-19-2010
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Here we demonstrate Au nanoparticle self-similar chain structure organized by triangle DNA origami with well-controlled orientation and <10 nm spacing. We show for the first time that a large DNA complex (origami) and multiple AuNP conjugates can be well-assembled and purified with reliable yields. The assembled structure could be used to generate high local-field enhancement. The same method can be used to precisely localize multiple components on a DNA template for potential applications in nanophotonic, nanomagnetic, and nanoelectronic devices.
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Band gap engineering of quaternary-alloyed ZnCdSSe quantum dots via a facile phosphine-free colloidal method.
J. Am. Chem. Soc.
PUBLISHED: 11-26-2009
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We demonstrate the synthesis of quaternary-alloyed Zn(x)Cd(1-x)S(y)Se(1-y) quantum dots (ZnCdSSe QQDs) across the entire composition range (x, y) = 0 to 1 with a size tunable from 4.0 to 10.0 nm by a facile, "green", phosphine-free, low-cost colloidal method. The ZnCdSSe QQDs have both composition- and size-dependent band gaps, which can be hybrid-engineered to span the entire visible spectrum. The new ZnCdSSe QQDs are easy to synthesize and have high quantum yields (up to 65%) without the necessity of overcoating a shell. These new quantum dots may find broad uses in biolabeling, biosensing, light-emitting diodes, and other nanodevice applications.
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Simple colloidal synthesis of single-crystal Sb-Se-S nanotubes with composition dependent band-gap energy in the near-infrared.
Nano Lett.
PUBLISHED: 04-28-2009
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We report the first synthesis of high-quality binary and ternary Sb(2)Se(3-x)S(x) nanotubes across the entire compositional range from x = 0 to 3 via a simple, low-cost, colloidal synthetic method of injection of Sb(III)-complex solution into a hot paraffin liquid containing Se, S, or a mixture thereof. In contrast to the classic rolling mechanism, the modular formation of the reported nanotubes follows a four-stage self-seeding process: (i) amorphous nanospheres, (ii) short crystalline nanotubes growing out of relatively large amorphous nanospheres, (iii) long crystalline nanotubes attached to small amorphous nanospheres, and (iv) single-crystal nanotubes. The obtained single-crystal nanotubes have tunable composition, orthorhombic phase, well-defined rectangular cross sections, and growth direction along [001], as revealed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and selected area electron diffraction studies. UV-vis-NIR absorption spectroscopy reveals that the optical bandgap energy of the Sb(2)Se(3-x)S(x) (0 < or = x < or = 3) nanotubes increases quadratically with the sulfur concentration x with these bandgap energies falling in the range from 1.18 to 1.63 eV at the red edge of the solar spectrum. The present study opens a new avenue to low-cost, large-scale synthesis of high quality semiconductor nanotubes with technological applications in solar energy conversion and also for a wide range of optical nanodevices operating in the near-infrared.
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Water-based route to ligand-selective synthesis of ZnSe and Cd-doped ZnSe quantum dots with tunable ultraviolet A to blue photoluminescence.
Langmuir
PUBLISHED: 02-28-2009
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A water-based route has been demonstrated for synthesizing ZnSe and Cd-doped ZnSe (Zn(x)Cd(1-x)Se, 0 < x < 1) quantum dots (QDs) that have tunable and narrow photoluminescence (PL) peaks from the ultraviolet A (UVA) to the blue range (350-490 nm) with full-width at half-maximum (fwhm) values of 24-36 nm. Hydrazine (N(2)H(4)) was used to maintain oxygen-free conditions, allowing the reaction vessel to be open to air. The properties of the QDs were controlled using the thiol ligands, 3-mercaptopropionic acid (MPA), thiolglycolic acid (TGA), and l-glutathione (GSH). On the basis of optical spectra, linear three-carbon MPA attenuated nucleation and growth, yielding small ZnSe QDs with a high density of surface defects. In contrast, TGA and GSH produced larger ZnSe QDs with lower surface defect densities. The absorption spectra show that growth was more uniform and better controlled with linear two-carbon TGA than branched bifunctional GSH. After 20 min of growth TGA-capped ZnSe had an average diameter of 2.5 nm based on high-resolution transmission electron microscopy images; these nanocrystals had an absorbance peak maximum of approximately 340 nm (3.65 eV) and a band gap PL emission peak at 372 nm (3.34 eV). Highly fluorescent Zn(x)Cd(1-x)Se QDs were fabricated by adding a Cd-thiol complex directly to ZnSe QD solutions; PL peaks were tuned in the blue range (400-490 nm) by changing the Zn to Cd ratio. The Cd-bearing nanocrystals contained proportionally more Se based on X-ray photoelectron spectroscopy, and Cd-Se bonds had ionic character, in contrast to primarily covalent Zn-Se bonds.
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Robust DNA-functionalized core/shell quantum dots with fluorescent emission spanning from UV-vis to near-IR and compatible with DNA-directed self-assembly.
J. Am. Chem. Soc.
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The assembly and isolation of DNA oligonucleotide-functionalized gold nanoparticles (AuNPs) has become a well-developed technology that is based on the strong bonding interactions between gold and thiolated DNA. However, achieving DNA-functionalized semiconductor quantum dots (QDs) that are robust enough to withstand precipitation at high temperature and ionic strength through simple attachment of modified DNA to the QD surface remains a challenge. We report the synthesis of stable core/shell (1-20 monolayers) QD-DNA conjugates in which the end of the phosphorothiolated oligonucleotide (5-10 nucleotides) is "embedded" within the shell of the QD. These reliable QD-DNA conjugates exhibit excellent chemical and photonic stability, colloidal stability over a wide pH range (4-12) and at high salt concentrations (>100 mM Na(+) or Mg(2+)), bright fluorescence emission with quantum yields of up to 70%, and broad spectral tunability with emission ranging from the UV to the NIR (360-800 nm).
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Solution synthesis of ultrathin single-crystalline SnS nanoribbons for photodetectors via phase transition and surface processing.
ACS Nano
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We report the solution-phase synthesis and surface processing of ~2-5 ?m long single-crystalline IV-VI tin(II) sulfide (SnS) ultrathin nanoribbons, with thicknesses down to 10 nm, and their use in single nanoribbon based photodetectors. The SnS nanoribbons grow via a metastable-to-stable phase transition from zinc blende (ZB) nanospheres to orthorhombic nanoribbons; dual-phase intermediate heterostructures with zinc blende nanosphere heads and orthorhombic nanoribbon tails were observed. Exchange of long, insulating organic oleylamine ligands by short, inorganic HS(-) ligands converts the organic SnS nanoribbons into completely inorganic, hydrophilic structures. Field-effect transistor (FET) devices were made from single SnS nanoribbons, both before and after ligand exchange, which exhibit p-type semiconductor behavior. The SnS single nanoribbon based photodetector devices showed highly sensitive and rapid photocurrent responses to illumination by blue, green, and red light. The switching behavior of photocurrent generation and annihilation is complete within approximately 1 ms and exhibits high photoconductivity gains (up to 2.3 × 10(4)) and good stability. The ON/OFF ratio of the photodetector can be engineered to 80 (4 nA/50 pA) using a small drain current (10 mV) for the all inorganic SnS nanoribbons. This work paves the way for the colloidal growth of low-cost, environmentally benign, single-crystalline narrow band gap semiconductor nanostructures from abundant elements for applications in photodetectors and other nanoscale devices.
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Aqueous synthesis of glutathione-capped CdTe/CdS/ZnS and CdTe/CdSe/ZnS core/shell/shell nanocrystal heterostructures.
Langmuir
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Here we demonstrate the aqueous synthesis of colloidal nanocrystal heterostructures consisting of the CdTe core encapsulated by CdS/ZnS or CdSe/ZnS shells using glutathione (GSH), a tripeptide, as the capping ligand. The inner CdTe/CdS and CdTe/CdSe heterostructures have type-I, quasi-type-II, or type-II band offsets depending on the core size and shell thickness, and the outer CdS/ZnS and CdSe/ZnS structures have type-I band offsets. The emission maxima of the assembled heterostructures were found to be dependent on the CdTe core size, with a wider range of spectral tunability observed for the smaller cores. Because of encapsulation effects, the formation of successive shells resulted in a considerable increase in the photoluminescence quantum yield; however, identifying optimal shell thicknesses was required to achieve the maximum quantum yield. Photoluminescence lifetime measurements revealed that the decrease in the quantum yield of thick-shell nanocrystals was caused by a substantial decrease in the radiative rate constant. By tuning the diameter of the core and the thickness of each shell, a broad range of high quantum yield (up to 45%) nanocrystal heterostructures with emission ranging from visible to NIR wavelengths (500-730 nm) were obtained. This versatile route to engineering the optical properties of nanocrystal heterostructures will provide new opportunities for applications in bioimaging and biolabeling.
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What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.